Carlos Rodriguez-Proenza1

1, Universidad Nacional Autonoma de Mexico, Querétaro, , Mexico

Understanding of thermodynamic and segregation mechanisms in bimetallic nanoparticles is of great significance for their use in catalysis and other applications. Molecular dynamics simulations, with the many-body-embeded atom model (EAM) potentials, were carried out in this work to study the thermodynamic properties and segregation mechanisms of core-shell and alloyed-(PtPd)923 -(AgPd)923 bimetallic nanoparticles during heating and freezing processes under the NVT assembly formalisms. In general, the results showed a trend of Pd and Ag atoms to segregate on the particle surfaces; for the PdPt systems Pt atoms are diffussed towards the inner of the particles while in the case of AgPd nanoparticles, Pd was the species that spread towards the interior. Similar results have been earlier reported and can be explained in terms of the surface energy of the involved species. The obtained results are corroborated both from the radial distribution functions, the statistical radius and temperature dependence of Pd, Ag and Pt number of atoms on the surface. Moreover, the corresponding temperature-dependent caloric curves, Lindemann index and heat capacity were plotted considering that they are three significant criteria for locating the melting and freezing points of nanoparticles. At the end of the cooling processes almost all nanoparticles showed a tendency to the formation of icosaedral nanostructures and it was corroborated from the calculation of the order parameter Q6 for each nanostructure.